In the related liquid crystal technology, each pixel consists of three subpixels in different colors, i.e., red (R), green (G) and blue (B) subpixels. For a red-green-blue-white (RGBW) technique, a white subpixel is added on the basis of the RGB subpixels, so a RGBW panel includes four subpixels in different colors. Due to such advantages as high brightness, low power consumption and low manufacture cost, the RGBW panel has quickly become a very popular product. However, due to the introduction of the white subpixel, the debugging of a grayscale voltage may be adversely affected to some extent, and the grayscale voltage of the RGBW panel may no longer be controlled by a Gamma Integrated Circuit (IC), i.e., a grayscale voltage debugging method for a RGB panel may no longer be applicable to the RGBW panel.